Coupling between transmitter and wave guide system



June 21, 1949. W G, TULLER v 2,473,834

. coUPLING BETWEEN TRANSMITTER AND WAVE GUIDE SYSTEM Filed Jan. 25, 1944 Patented June 21, 1949 COUPLING BETWEEN TRANSMITTER AND WAVE GUIDE SYSTEM William G. Tuller, Watertown, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application January 25, 1944, Serial No. 519,682 Y 8 Claims.

This invention relates to guided electromagnetic wave transmission, and more specifically to a means providing a fluid-tight seal for guided' wave transmission lines to prevent the entrance of moisture, or other foreign matter, to the line or other parts of the system, such as the transmitter and receiver.

In many installations of ultra high frequency equipment, for example on ships, it is desirable to completely enclose the transmitter, the receiver, or both, in a huid-tight housing to prevent the entrance of moisture or other foreign matter which would adversely aect the operation of the system, or its durability. Since in such installations the wave guide must pass through the housing, a sealed connection must be made between the portion of the wave guide within the housing and the portion exterior thereto leading to the antenna, otherwise fluid or other foreign matter may enter the system at the joint between these two portions. It is desirable to permit a slight relative motion between the sections of the wave guide leading to the antenna and the sections within the housing containing the transmitting equipment. However, iff this is eiected by leaving a slight clearance between the section of the wave guide within the housing and the portion exterior thereto, the value of the housing is nulliied since moisture or other foreign matter may enter through this clearance.

It is an object of this invention to provide a structure which will permit slight relative movements of the housing of such a system relative to the portion of the wave guide exterior thereto,

and which at the same time provides a fluid-tight connection without introducing material electrical losses or otherwise impairing the eiciency or durability of the transmission line or the transmitting system with which it is associated.

It is a further object of the invention to provide a device of the type described which will permit the transmission of ultra-high frequency oscillations without decreasing the available band width to which the system isfresponsive.

The above and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunc-y tion with the accompanying drawing in which:

Fig. 1 represents a longitudinal section through aA huid-tight joint for a guided wave transmission line constructed in accordance with the present invention;

Fig. 2 represents on a reduced scale a section taken on the line 2-2 of Fig. 1; and

Fig. 3 shows a set of curves which in a general qualitative way illustrate certain operating characteristics of the present invention,

In the drawing, reference numeral I indicates a portion ci a guided wave transmission line within the housing 2 of a transmitting system indicated diagrammatically at 3. It wil1 be understood that the system 3 may include various elements such as the receiving system or portions thereof, and any other elements which it is desired to protect, as well as the transmitter.

In the instance shown, the wave guide section I is of rectangular cross-section, but it will be understood that the invention may be applied to guided wave transmission systems having' transmission lines of other types. A coupling flange II mounted upon the end of the wave guide section I, as for example by soldering, is provided with a rectangular opening 5 in the central portion thereof, which opening is of somewhat less length than the greatest transverse dimension of the wave guide and of substantially the same width as the narrowest dimension of said wave guide. Accordingly, the open end of the section I is partially obstructed by the portions 6 of the flange 4 overlying the section I.

The section I is supported from the chassis of the transmitter v3 independently of the housing 2, so that this housing may be readily removed from the transmitter structure and the associated Wave guide section I.

The housing 2 is provided with a circular opening 'I adjacent to and of somewhat greater diameter than the diameter of the flange 1I. The opening l is closed by a sealing structure cornprising a tubular member 8 having an intermediate inwardly indented portion 9. The tubular member 3 is of metal, such as brass, and is bent inwardly on each side of the intermediate indented portion 9 to provide shouldered portions !D and II adjacent the upper and lower ends thereof, respectively. An upwardly projecting rim I2 extends for a short distance from the upper shouldered portion Ill and a similar rim I3 projects downwardly from the lower shouldered portion II. A series of openings III are provided adjacent the periphery of the upper shouldered portion Il), and similar openings I5, in alignment with the openings I4, are provided in the lower shouldered portion I I.

A wave guide section I6, having substantially the same transverse dimensions as the wave guide section I, is positioned centrally within the tubular structure 8 and maintained in position relative thereto by means of coupling flanges I'I and I8 fixed to the upper and lower ends, respectively, of the wave guide section I6, as, for example, by soldering. The flange I'I is provided with a downwardly projecting rim I9 at the outer' peripheral; edge thereof, whichrirn is soldered to the upwardly projecting rim I2 of! the tubular member 8. rl'he lower coupling flange I8 is provided with an upwardly projecting rim 2D at its outer peripheral edge. adapted` to be soldered or otherwise fixed to the downwardly projecting rim I3 of the tubular member 3'. The

flange I8 is provided with Stn-annular! reentra'nt what less length thanl the longer dimension of.'

the wave guide section' I3, so that'the wave gui'd'e section I6 is partiallyobstructed' by strips 23- in the same manner that the wave guide section iIi is partially obstructed by' the projecting strips A4 sheet of polystyrene or similar insulatinga material 24 closes the opening 22 at' the upper end ofthe wave guide section I3, said sheet being of suflcient diameter` tocover the'v flange I'lf and extend downwardly about the peripheral` rim I9 thereof andithenceoutwardly across the upper shouldered portionl I-Df. A1 similar sheet of insulating material 25y closes the lower end of: the wave guide section I 6 and is'fbent upwardly and' outwardly adjacent its peripheral edge to"y conform to the lower shoulderedportion II. Thesheets of insulating material 24 andv 25 are secured in position flush withY the outer surfacesA of the flanges I1 and l8'by means of tie rods 26 which extendt through perforations adjacent" the peripheraledge of` thesheets'y 24 and25 and' through the' openings I4`-and I5'in the shouldered portions I"and` I I'. Thetie rods 2B`are provided at one end with heads 2'!` which bear upon a clamping ring 28: and are provided at thev opposite' ends thereof with nut's29 which maybe screwed on the threaded ends of the tie rods,

which ends project through' perforations in the housing 2 adja'centth'ev opening 'I'. If desired, a;-

gasket 30 of' cork or other suitable materialmay be interposedA between the clamping. ring` 28- and the sheet 24 andla similar gasket 3l may be interposed betweenvthe housing 2and the sheet 25.

It-will be evident :that for the purpose ofsealing the housingv 2S againstthe entrance of moisture andother foreign mattenit wouldbe sufcientto provide but one of the insulating sheets 24'or 25 closing one end or the other of the wave guide section I 6; I- have found, however, thatf if: two suchV insulating: sheets are utilized andi` these are properly' spaced, as hereinafter de scribed, then' the-width of available wave band; which the system is capable oftransmitting, is materially increased over the width of the band' which would be transmitted if vbut a single'insulating sheet were used. Thus, if 'the length of .wavef :-are1spaceda distancei substantially equal to'f` ,4 undue attenuation is substantially 30 per cent greater than if but a single sheet were used.

The advantage to be derived from the use of two sheets of the insulating material spaced as described will be better appreciated after a consideration of the set of curves shown in Fig. 3, in which the curve S represents in: a general qualitative manner the relative amount of the reflection R as plotted against the frequency f,

when a single sheet of insulating material such as 24.01125 is usedA in a system of the type described'. The curve T represents the correspondi'ng relative values of R and f when two such sheets 24 and 25' are. utilized and spaced at a distance substantially equal to one-quarter of the length ofthe'wave on the transmission line or any odd multiple of a quarter of such wave length. From these curves it will be seen that ifv thetarea below the level h represents a region in which the reection R is sufficiently low to befpermissable, then frequencies within the range A may beY utilizedv in ar systemf provided.v with the: preferred form of the seal in which the two sheets 247' and 25 are spaced as described, while only frequencies within the rangeB, which is-approxi mately '70l per cent' of A, could be utilized in a`A system provided with only one such'sheet'.

A wave guide section 32 leadingtothe antenna isprovided withl a coupling flange 33 coacting with the flange I'I. structurally the coupling flange 33'is similar to the coupling ange landf ispreferably positioned in al plane parallel toi the plane of the sheet 24, and-spaced therefrom:

at a` distancel ofV about one-eightlitol one-quarter inch.

A` flexible ange 34, preferably of: rubber or similar material, issecured upon the wave guide` 32 ata point' abovethe coupling'ange 33. The flexible flange 34 isprovided' with-anoutwardly flaringv portion sufficiently large to enclose the couplingflange 33 and the'upper part ofthe tubular member 8, and--terminates in an inwardly projecting. rim 35 adapted to contract into the indented portion- 9l of the tubular member I3,.thusy providing aexibleluid-tight shield between the wave guide section 32 and the tubular membery 8; This construction-permits small relativev displacements-between the waveguide section 32 leading to the antenna, and the wave guide section I6v which is fixed relative to the housing 2.

In operation, at the frequencies at which systemsof this type are designed to function, I have found that the sheets 24 and 25 introduce a capacity effect which would not otherwisel be present in the system, although the material from which the sheets are constructed. possesses the mosty desirable characteristics of any material available. I have found that by providing the strips of conductive material 6 and 23 overlying and partially obstructing the wavev guide, an inductance is provided which in any given instance may be made suicient to match the capacitance of the sheets of insulating material;

It will be observed that the sealing structure comprisingl the tubular member 8 and the parts rigidly connected thereto may be assembled as a unit, and when this unitv is secured to thehousing structure 2 by the tie rods 26 the parts enclosed by said housing. are completely sealed regardless of whether or4 not the device is connected to the section 32 of the antenna system. Thus, the transmitter and associated parts are sealed' against the entrance of foreign matter 7 ,while the same are being shipped' or stored independently of the antenna system', and yet are in condition for immediate connection to the antenna system, which is usually separately assembled and supported, by merely sliding the housing into position adjacent the section 32. The exible ange 34 is not essential in all instances, but is desirable where the system is so exposed that moisture or other foreign matter may be deposited on the face of the sheet 24 to an extent suflicient to introduce an undesirable impedance across the wave guide due to the electrical characteristics of the deposit. However, when used, the ange 34 may' be readily flexed into position with the rim 34 stretched to resiliently engage the indented portion 9 of the tubular member 8.

It will be understood that the invention is not limited to the particular details as described above as many equivalents will suggest themselves to those skilled in the art. It is therefore desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

It will also be understood that by the expression a distance substantially equal to an odd multiple of one-quarter of the length of the wave on the wave guide and similar expressions as used in the appended claims, I intend to include the fundamental instance in which the distance is one-quarter of the wave length, the odd multiple being one.

What is claimed is:

1. A guided wave transmission system including in combination a transmitter, a housing enclosing said transmitter, a wave guide section connected to said transmitter and terminating adjacent an opening in said housing, a second wave guide section in registry with said firstmentioned section, a sheet of insulating material extending across said second wave guide section, said second section being spaced from said first-mentioned section and supported by said housing, a third wave guide section on the exterior of said housing spaced from and adapted to register with said second wave guide section, said third wave guide section being supported independently of said housing, and a flexible flange enclosing the gap between said second wave guide section and said third wave guide section.

2. A guided wave transmission system including in combination a transmitter, a housing enclosing said transmitter, a wave guide section connected to said transmitter and terminating adjacent an opening in said housing, a second wave guide section in registry with said iirst-mentioned section, a pair of sheets of insulating material extending across each end of said second wave guide section, said second section being spaced from said first-mentioned section and supported by said housing, a third wave guide section on the exterior of said housing spaced from and adapted to register with said second wave guide section, said third wave guide section being supported independently of said housing, and a flexible flange enclosing the gap between said second wave guide section and said third wave guide section.

3. A guided wave transmission system including in combination a transmitter, a housing enclosing said transmitter, a wave guide section connected to said transmitter and terminating adjacent an opening in said housing, a second wave guide section in registry with said firstmentioned section, a pair of sheets of insulating material extending across each end of said second wave guide section, said sheets of insulating material being spaced from each other a distance substantially equal to an odd multiple of one-y quarter of the length of the wave on the transmission system, a third wave guide section on the exterior of said housing spaced from and adapted to register with said second wave guide section, said third wave guide section being supported independently of said housing.

4. A guided wave transmission system including in combination a transmitter, a housing enclosing said transmitter, a wave guide section connected to said transmitter and terminating adjacent an opening in said housing, a second Wave guide section in registry with said rstm-entioned section, a pair of sheets of insulating material extending across each end of said second wave guide section, said sheets of insulating material being spaced from each other a distance substantially equal to an odd multiple of onequarter of the length of the wave on the transmission system, a third wave guide section on the exterior of said housing spaced from and adapted to register with said second wave guide section, said third wave guide section being supported independently of said housing, and a flexible flange enclosing the gap between said second wave guide section and said third wave guide section.

5. A wave guide system for high-frequency electromagnetic waves including two wave guide sections, a third wave guide section, said third wave guide section having a length approximately equal to one-quarter of the length of the waves adapted to be transmitted by said system, said two wave guide sections being spaced by a distance slightly greater than the length of said third section whereby said third section is freely insertable therebetween, sheets of insulating material one extending across each end of said third wave guide section, and means to support said third wave guide section in spaced relation to each of said two wave guide sections.

6. A wave guide system for high-frequency electromagnetic waves including two wave guide sections, a third wave guide section detachably mounted between said two sections, said third wave guide section having a length approximately equal to one-quarter of the length of the waves adapted to be transmitted by said system, sheets of insulating material one extending across each end of said third wave guide section, and movable means enclosing the junction between one of said two wave guide sections and said third section.

7. A wave guide system for high-frequency electromagnet waves including two wave guide sections, a third wave guide section, said third wave guide section having a length approximately equal to one-quarter of the length of the waves adapted to be transmitted by said system, means to support said third wave guide section between and spaced from each of said two Wave guide sections by a short gap, sheets of insulating material one extending across each end of said third wave guide section, and a flexible flange enclosing the gap between one of said two wave guide sections and said third section.

8. A wave guide system for high-frequency electromagnetic waves including two wave guide sections, a third wave guide section, said third wave guide section having a length approximately equal to one-quarter of the length of the waves adapted to be transmitted by said system, means to support said third wave guide section between and spaced from at least one of said two wave guide sections by a short gap, sheets of insulating material one extending across each end of said REFERENCES' CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,541,601 Tribe June 9, 1925 2,129,713 Southworth Sept. 13, 1938 Number Certificate of Correction Patent No. 2,473,834. June 21, 1949.

WILLIAM G. TULLER It is hereby certified that errors appear in the printed speeioation of the above numbered patent requiring correction as follows:

Column 4, line 21, for permissable read permissible; column 6, lines 53 and 54, claim 7, for eleetromagnet read electromagnetic;

and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Of'uee.

Signed and sealed this 22nd day of November, A. D. 1949.

[SEAL] THOMAS F. MURPHY,

Assistant 'ommz'ssoner of Patents. 

